The main components of a drive-train are a drive aggregate and a transmission. The transmission converts rotational speeds and torques, and transmits a traction force provided by the drive aggregate to a drive output of the drive-train. The present invention concerns a method for operating a drive-train having a drive aggregate in the form of a hybrid drive unit and at least one auxiliary power takeoff on the transmission side or on the drive aggregate side.
The hybrid drive unit of such a drive-train comprises an internal combustion engine and an electric machine, the electric machine of the hybrid drive unit can be operated as a generator or as a motor. When the electric machine of the hybrid drive unit is operating as a generator, an electrical energy accumulator of the drive-train is predominantly charged, and when the electric machine of the hybrid drive unit is operated as a motor the electrical energy accumulator of the drive-train is predominantly discharged.
An auxiliary drive, also known as an auxiliary power takeoff (PTO), draws power from the transmission side or from the drive aggregate side, this power then not being available at the drive output as traction force. An auxiliary power takeoff can be used, for example, for a cooling aggregate of a refrigerator vehicle or for a hydraulic press of a garbage disposal vehicle or for a hydraulically operated crane of a utility vehicle, or the like.
Until now it has been difficult to operate a drive-train with a hybrid drive unit and at least one auxiliary power takeoff in an efficient manner.